1. Field of the Invention
The present invention relates to equipment for drying refuse and the like.
2. Description of the Related Art
Japanese Utility Model Publication No. 16877/69 and Japanese Patent Publication No. 55119/82 disclose examples of vacuum drying equipment, in which the internal pressure of a vessel which contains a material to be dried is reduced by vacuum to lower the boiling point of the material. A heat pump is used to heat the vessel to evaporate moisture from the material to be dried, and the evaporated moisture is condensed into water by refrigeration generated by the heat pump. The condensed water is then discharged to the exterior of the equipment.
In the vacuum drying equipment disclosed in the above publications, however, no consideration is given to the case where the article to be dried is left standing for a long time in the drying vessel before drying is performed. The aforementioned situation gives rise to problems when such vacuum drying apparatus are used for the drying of refuse, but no measures have been taken to address articles which are not dried right away.
With conventional drying equipment, drying is not always performed immediately after introduction of refuse into the drying vessel. Rather, refuse is often introduced incrementally several times throughout the day and then is dried cumulatively at a single time in the evening. Further, when the amount of refuse is small, the refuse is sometimes not even dried daily, but is heaped up without treatment until a predetermined amount is reached, and then the refuse which has been heaped up two or three days is dried cumulatively at one time.
Therefore, when the outdoor temperature is high, for example in the summertime, refuse which has been introduced into the drying vessel in the morning will rot to some extent, so that an offensive smell is dissipated to the exterior of the equipment at every opening of the inlet.
Further, if rotten refuse is dried in the equipment, volatile organic substances such as, for example, ammonia, methyl mercaptan, trimethylamine and hydrogen sulfide will be mixed into the waste water discharged to the exterior of the equipment, so that the problem of offensive smell arises also with respect to the waste water.